A cathode ray tube (CRT) converts information contained in an input signal to electron beam energy and converts that energy into light energy to provide a visual information output on a phosphorous screen. The amount of beam modulation of the CRT and thus, the amount of light output of the CRT is a function of the voltage difference between the cathode and the first grid of the CRT (the grid closest to the cathode). If the voltage of the first grid of the CRT is held constant, then the cathode may be modulated with the voltage that represents the video information i.e. the input signal. In the event the voltage on the cathode is held constant then the voltage on the first grid may be modulated with the voltage that, represents the video information i.e. the CRT input signal.
A CRT video amplifier drive circuit provides blanking of the CRT input signal during the horizontal and vertical retrace periods i.e. the time the electron beam returns to its starting point for scanning a horizontal line and the time the electron beam returns to its starting point for scanning the image vertically. The aforementioned circuit also amplifies and processes the video information and applies it to the cathode or the first grid.
Photographic printers have been utilized that use a CRT as an imaging source for producing a print on a photosensitive media. A monochromatic or color CRT may be used as a imaging source and a monochromatic or color photosensitive media such as photosensitive paper or film may be used to record the CRT produced image. Typically a monochromatic image is displayed on the phosphorous screen of a CRT by modulating the electron beam of the CRT with dark to light gradations of the image and simultaneously deflecting the CRT electron beam to achieve the position of the pixels on the CRT screen. The image on the screen of the CRT may be transferred to the photographic media by any known means i.e. contact printing (the photographic media is placed directly on the CRT screen), projected by one or more lenses and/or one or more mirrors.
A monochromatic CRT may be used to display a color picture on a photographic media. When a monochromatic display is used, three sequential exposures through red, green and blue filters will individually expose the photographic media to the red, green and blue components of the image displayed on the screen of the CRT.
A color CRT may also be used to display a color picture on a photographic media. If a color CRT was used, the color CRT would expose in one sequence the red, green and blue portions of the image on the screen of the CRT simultaneously onto the photographic media.